U.S. patent application number 10/773289 was filed with the patent office on 2004-08-12 for ink-jet printhead and method for manufacturing the same.
Invention is credited to Cho, Chang-ho, Kuk, Keon, Oh, Yong-soo, Shin, Jong-woo.
Application Number | 20040155930 10/773289 |
Document ID | / |
Family ID | 32677864 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040155930 |
Kind Code |
A1 |
Cho, Chang-ho ; et
al. |
August 12, 2004 |
Ink-jet printhead and method for manufacturing the same
Abstract
In an ink-jet printhead and a method for manufacturing the same,
the ink-jet printhead includes a substrate, an ink chamber to be
filled with ink to be ejected formed on an upper surface of the
substrate, a restrictor, which is a path through which ink is
supplied from an ink reservoir to the ink chamber, perforating a
bottom surface of the substrate and a bottom surface of the ink
chamber, a nozzle plate, which is stacked on the upper surface of
the substrate and forms an upper wall of the ink chamber, a nozzle
perforating the nozzle plate at a position corresponding to a
center of the ink chamber, a heater formed in the nozzle plate to
surround the nozzle, and a conductor for applying a current to the
heater.
Inventors: |
Cho, Chang-ho; (Suwon-si,
KR) ; Oh, Yong-soo; (Seongnam-si, KR) ; Kuk,
Keon; (Yongin-si, KR) ; Shin, Jong-woo;
(Suwon-si, KR) |
Correspondence
Address: |
LEE & STERBA, P.C.
1101 Wilson Boulevard, Suite 2000
Arlington
VA
22209
US
|
Family ID: |
32677864 |
Appl. No.: |
10/773289 |
Filed: |
February 9, 2004 |
Current U.S.
Class: |
347/56 |
Current CPC
Class: |
B41J 2/1629 20130101;
B41J 2/1404 20130101; B41J 2/14137 20130101; B41J 2/1643 20130101;
B41J 2/1601 20130101; B41J 2002/1437 20130101; B41J 2/1631
20130101 |
Class at
Publication: |
347/056 |
International
Class: |
B41J 002/05 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 8, 2003 |
KR |
2003-8005 |
Claims
What is claimed is:
1. An ink-jet printhead, comprising: a substrate; an ink chamber to
be filled with ink to be ejected formed on an upper surface of the
substrate; a restrictor, which is a path through which ink is
supplied from an ink reservoir to the ink chamber, perforating a
bottom surface of the substrate and a bottom surface of the ink
chamber; a nozzle plate, which is stacked on the upper surface of
the substrate and forms an upper wall of the ink chamber; a nozzle
perforating the nozzle plate at a position corresponding to a
center of the ink chamber; a heater formed in the nozzle plate to
surround the nozzle; and a conductor for applying a current to the
heater.
2. The ink-jet printhead as claimed in claim 1, wherein the
restrictor has a length of about 200-750 .mu.m.
3. The ink-jet printhead as claimed in claim 1, wherein the heater
surrounds the nozzle.
4. The ink-jet printhead as claimed in claim 3, wherein the heater
is formed of one material selected from the group consisting of
TaAl, TiN, CrN, W, and polysilicon.
5. The ink-jet printhead as claimed in claim 1, wherein the
conductor is formed of aluminum or an aluminum alloy.
6. The ink-jet printhead as claimed in claim 1, wherein the nozzle
plate includes a plurality of passivation layers.
7. The ink-jet printhead as claimed in claim 6, wherein the
plurality of passivation layers includes a first passivation layer,
a second passivation layer, and a third passivation layer, which
are sequentially stacked on the substrate, and wherein the heater
is disposed between the first passivation layer and the second
passivation layer, and the conductor is disposed between the second
passivation layer and the third passivation layer.
8. The ink-jet printhead as claimed in claim 6, wherein each of the
plurality of passivation layers is formed of at least one material
selected from the group consisting of SiO.sub.2, Si.sub.3N.sub.4,
SiC, Ta, Pd, Au, TaO, TaN, Ti, TiN, Al.sub.2O.sub.3, CrN, and
RuO.sub.2.
9. The ink-jet printhead as claimed in claim 6, wherein the nozzle
plate further includes a heat dissipating layer stacked on the
plurality of passivation layers.
10. The ink-jet printhead as claimed in claim 9, wherein the heat
dissipating layer defines an upper portion of the nozzle and is
formed of a metallic material having thermal conductivity to
dissipate heat generated by the heater and heat remaining around
the heater.
11. The ink-jet printhead as claimed in claim 10, wherein the heat
dissipating layer is formed of at least one material selected from
the group consisting of Ni, Fe, Au, Pd, and Cu.
12. The ink-jet printhead as claimed in claim 9, wherein the heat
dissipating layer has a thickness greater than about 10 .mu.m.
13. A method for manufacturing an ink-jet printhead, comprising:
(a) preparing a substrate; (b) sequentially stacking a plurality of
passivation layers on the substrate and forming a heater and a
conductor connected to the heater between adjacent passivation
layers; (c) forming a heat dissipating layer on the plurality of
passivation layers and forming a nozzle perforating the passivation
layers and the heat dissipating layer; (d) etching a bottom surface
of the substrate and forming a restrictor in communication with an
ink reservoir; and (e) etching the substrate exposed through the
nozzle to be in communication with the restrictor and forming an
ink chamber to be filled with ink.
14. The method as claimed in claim 13, wherein sequentially
stacking the plurality of passivation layers on the substrate and
forming the heater and the conductor connected to the heater
between adjacent passivation layers comprises: forming a first
passivation layer on an upper surface of the substrate; forming the
heater on the first passivation layer; forming a second passivation
layer on the first passivation layer and the heater; forming the
conductor on the second passivation layer; and forming a third
passivation layer on the second passivation layer and the
conductor.
15. The method as claimed in claim 13, wherein forming the heat
dissipating layer on the plurality of passivation layers and
forming the nozzle perforating the plurality of passivation layers
and the heat dissipating layer comprises: patterning the plurality
of passivation layers and exposing an upper surface of the
substrate; forming a sacrificial layer for forming the nozzle on
the exposed substrate; forming a heat dissipating layer on the
plurality of passivation layers; and removing the sacrificial layer
and forming the nozzle.
16. The method as claimed in claim 15, wherein the sacrificial
layer is formed of a photoresist.
17. The method as claimed in claim 15, wherein the heat dissipating
layer is formed by electroplating.
18. The method as claimed in claim 15, wherein the heat dissipating
layer has a thickness greater than about 10 .mu.m.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an ink-jet printhead and a
method for manufacturing the same. More particularly, the present
invention relates to an ink-jet printhead having improved
efficiency and performance, and a method for manufacturing the
same.
[0003] 2. Description of the Related Art
[0004] Typically, ink-jet printheads are devices for printing a
predetermined image, color or black, by ejecting a small volume
droplet of printing ink at a desired position on a recording sheet.
Ink-jet printheads are largely categorized into two types depending
on which ink droplet ejection mechanism is used. A first type is a
thermally driven ink-jet printhead in which a heat source is
employed to form and expand bubbles in ink causing ink droplets to
be ejected. A second type is a piezoelectrically driven ink-jet
printhead in which a piezoelectric material deforms to exert
pressure on ink causing ink droplets to be ejected.
[0005] Hereinafter, the ink ejection mechanism in the thermally
driven ink-jet printhead will be described in greater detail. When
a pulse current flows through a heater formed of a resistance
heating material, the heater generates heat and ink adjacent to the
heater is instantaneously heated to about 300.degree. C., thereby
boiling the ink. The boiling of the ink causes bubbles to be
generated, expand, and apply pressure to an interior of an ink
chamber filled with ink. As a result, ink near a nozzle is ejected
from the ink chamber in droplet form through the nozzle.
[0006] The thermal driving method includes a top-shooting method, a
side-shooting method, and a back-shooting method depending on a
growth direction of bubbles and an ejection direction of ink
droplets.
[0007] The top-shooting method is a method in which the growth
direction of bubbles is the same as the ejection direction of ink
droplets. The side-shooting method is a method in which the growth
direction of bubbles is perpendicular to the ejection direction of
ink droplets. The back-shooting method is a method in which the
growth direction of bubbles is opposite to the ejection direction
of ink droplets.
[0008] The ink-jet printheads using the thermal driving method
should satisfy the following requirements. First, manufacturing of
the ink-jet printheads should be simple, costs should be low, and
should facilitate mass production thereof. Second, in order to
obtain a high-quality image, cross talk between adjacent nozzles
should be suppressed while a distance between adjacent nozzles
should be narrow; that is, in order to increase dots per inch
(DPI), a plurality of nozzles should be densely positioned. Third,
in order to perform a high-speed printing operation, a period in
which the ink chamber is refilled with ink after being ejected from
the ink chamber should be as short as possible and the cooling of
heated ink and heater should be performed quickly to increase a
driving frequency.
[0009] FIGS. 1 through 4 illustrate various structures of
conventional ink-jet printheads using the back-shooting method.
[0010] FIG. 1 illustrates a separated perspective view of a
conventional ink-jet printhead. Referring to FIG. 1, the ink-jet
printhead has a structure in which a substrate 36, on which a
nozzle 32 and an ink chamber 34 are formed, is stacked on an ink
reservoir 30, in which an ink supply conduit 31 is formed. In this
printhead, a heater is disposed around the nozzle 32, although the
heater is not shown in FIG. 1.
[0011] In the above structure, when a pulse current is applied to
the heater and the heater generates heat, ink in the ink chamber 34
is boiled, and bubbles are generated. The bubbles expand
continuously and apply a pressure to ink in the ink chamber 34.
This pressure causes ink to be ejected in droplet form through the
nozzle 32.
[0012] In the ink-jet printhead using the back-shooting method, in
order to effectively use energy of a bubble in a direction of ink
ejection, flow resistance should be large so that the flow of ink
is suppressed in a direction of bubble growth.
[0013] However, an element of the printhead for creating flow
resistance between the ink chamber 34 and the ink reservoir 30 does
not exist in the aforementioned inkjet printhead. Accordingly, flow
in the direction of bubble growth cannot be restricted. Thus, a
larger amount of energy is required to be generated in the
direction of bubble growth in order to eject ink. In addition,
since a height of the ink chamber 34 is almost the same as a
thickness of the substrate 36, a size of the ink chamber 34 is
increased unless a very thin substrate is used. As a result, an
amount of ink affected by bubbles is increased. This means that an
inertia force of ink is increased, and an operating frequency of
the printhead is restricted by the inertia force of ink.
[0014] FIG. 2 illustrates a cross-sectional view of a structure of
another conventional ink-jet printhead. Referring to FIG. 2, a
nozzle 42 is formed at one end of an ink channel 40 through which
ink flows, and a heater 44 is disposed around the nozzle 42. The
ink channel 40 has a shape such that a sectional area thereof
gradually increases in a direction of bubble growth.
[0015] In the aforementioned ink-jet printhead, flow resistance is
reduced in the direction of bubble growth. Accordingly, a larger
bubble energy is required to eject ink.
[0016] FIG. 3 illustrates a cross-sectional view of another
structure of a conventional ink-jet printhead. Referring to FIG. 3,
a substantially hemispheric ink chamber 50 is formed in a substrate
65, and a manifold 54 for supplying ink to the ink chamber 50 is
formed under the substrate 65. An ink channel 52 for providing
communication between the ink chamber 50 and the manifold 54 is
formed on a bottom center of the ink chamber 50. A nozzle plate 60,
in which a nozzle 58 is formed, is stacked on a top surface of the
substrate 65. The nozzle plate 60 forms an upper wall of the ink
chamber 50. A heater 56 is formed in the nozzle plate 60 and
surrounds the nozzle 58.
[0017] FIG. 4 illustrates a cross-sectional view of a structure of
yet another conventional ink-jet printhead. Referring to FIG. 4, an
ink chamber 72, which has a substantially hemispherical shape and
is to be filled with ink, and an ink channel 74, which is formed to
a smaller depth than the ink chamber 72 and supplies ink to the ink
chamber 72, are formed on a surface of a substrate 70. A manifold
76 for supplying ink to the ink channel 74 is formed on a bottom
surface of the substrate 70. A nozzle plate 80 formed of a
plurality of material layers is stacked on an upper surface of the
substrate 70 and forms an upper wall of the ink chamber 72. A
nozzle 78, through which ink is ejected, is formed in a position of
the nozzle plate 80 corresponding to a center of the ink chamber
72. A ring-shaped heater 82 is formed around the nozzle 78 and
surrounds the nozzle 78. A nozzle guide 84 is additionally formed
in this printhead. The nozzle guide 84 guides an ejection direction
of ink and ejects ink droplets to be precisely perpendicular to the
upper surface of the substrate 70.
[0018] As described above, the conventional ink-jet printheads
shown in FIGS. 3 and 4 have a structure in which a manifold is
formed between an ink channel and an ink reservoir. However, in the
previous ink-jet printhead, it is not easy to process an ink
channel. In addition, even though the ink channel may be processed,
there is a limitation on a shape of the ink channel or there may be
an error between processed ink channels.
[0019] When the ink channel is processed on the substrate, there is
a limitation on the shape of the ink channel. More specifically,
the shape of the nozzle is transferred to the shape of the ink
channel using a method of processing an ink channel on the
substrate. In general, flow resistance of a conduit is proportional
to a length of the conduit and is inversely proportional to the
square of a sectional area of the conduit. Flow resistance can be
adjusted by adjusting the length of the conduit. However, it is
difficult to adjust a flow resistance ratio of a nozzle and an ink
channel that determine the performance of the ink-jet printhead
using the back-shooting method because of requirements on those
dimensions. Specifically, the length of the nozzle should be
sufficiently long so that ink is stably ejected. In this case, the
length of the ink channel should be sufficiently long. If the ink
channel is processed through the nozzle, a processing time is
increased. In addition, as the processing time is increased, the
etching amount of a passivation layer formed under a heater is
gradually increased. Thus, the thickness of the passivation layer
should be excessively large.
[0020] When the ink channel is processed under the substrate, due
to a step of a manifold, it is difficult to process the ink
channel, and even though the ink channel may be processed, there
may be an error between processed ink channels. In addition, the
depth of the manifold is generally greater than 400 .mu.m. In a
structure having a large step, it is difficult to perform a
photolithography process using an existing semiconductor device.
First, when coating a photoresist, a photoresist that can be plated
should be used, or a specific device, such as a spray coater,
should be used. When exposing the photoresist, a specific device,
such as a reconstructed projection aligner, and not a general
exposure device, should be used. Further, even though the ink
channel is processed using the aforementioned method, there is a
larger error than in processing in which there is no step of the
manifold. Since flow resistance is inversely proportional to the
square of a sectional area of a conduit, even a small error in
processing of the ink channel affects the performance of the
ink-jet printhead.
SUMMARY OF THE INVENTION
[0021] The present invention provides an ink-jet printhead having
improved efficiency and performance, and a method for manufacturing
the same.
[0022] According to a feature of an embodiment of the present
invention, there is provided an ink-jet printhead including a
substrate, an ink chamber to be filled with ink to be ejected
formed on an upper surface of the substrate, a restrictor, which is
a path through which ink is supplied from an ink reservoir to the
ink chamber, perforating a bottom surface of the substrate and a
bottom surface of the ink chamber, a nozzle plate, which is stacked
on the upper surface of the substrate and forms an upper wall of
the ink chamber, a nozzle perforating the nozzle plate at a
position corresponding to a center of the ink chamber, a heater
formed in the nozzle plate to surround the nozzle, and a conductor
for applying a current to the heater.
[0023] Preferably, the restrictor has a length of about 200-750
.mu.m.
[0024] The heater may surround the nozzle and may be formed of one
material selected from the group consisting of TaAl, TiN, CrN, W,
and polysilicon. The conductor may be formed of aluminum or an
aluminum alloy.
[0025] The nozzle plate may include a plurality of passivation
layers. Here, the plurality of passivation layers may include a
first passivation layer, a second passivation layer, and a third
passivation layer, which are sequentially stacked on the substrate,
and the heater may be disposed between the first passivation layer
and the second passivation layer, and the conductor may be disposed
between the second passivation layer and the third passivation
layer. The passivation layers may be formed of at least one
material selected from the group consisting of SiO.sub.2,
Si.sub.3N.sub.4, SiC, Ta, Pd, Au, TaO, TaN, Ti, TiN,
Al.sub.2O.sub.3, CrN, or RuO.sub.2.
[0026] The nozzle plate may further include a heat dissipating
layer stacked on the plurality of passivation layers. Here, the
heat dissipating layer may define an upper portion of the nozzle
and may be formed of a metallic material having thermal
conductivity to dissipate heat generated by the heater and heat
remaining around the heater. The heat dissipating layer may be
formed of at least one material selected from the group consisting
of Ni, Fe, Au, Pd, and Cu, and the thickness of the heat
dissipating layer may be greater than 10 .mu.m.
[0027] According to another feature of an embodiment of the present
invention, there is provided a method for manufacturing an ink-jet
printhead including preparing a substrate, sequentially stacking a
plurality of passivation layers on the substrate and forming a
heater and a conductor connected to the heater between adjacent
passivation layers, forming a heat dissipating layer on the
plurality of passivation layers and forming a nozzle perforating
the passivation layers and the heat dissipating layer, etching a
bottom surface of the substrate and forming a restrictor in
communication with an ink reservoir, and etching the substrate
exposed through the nozzle to be in communication with the
restrictor and forming an ink chamber to be filled with ink.
[0028] Here, sequentially stacking the plurality of passivation
layers on the substrate and forming the heater and the conductor
connected to the heater between adjacent passivation layers may
include forming a first passivation layer on an upper surface of
the substrate, forming the heater on the first passivation layer,
forming a second passivation layer on the first passivation layer
and the heater, forming the conductor on the second passivation
layer, and forming a third passivation layer on the second
passivation layer and the conductor.
[0029] In addition, forming the heat dissipating layer on the
plurality of passivation layers and forming the nozzle perforating
the plurality of passivation layers and the heat dissipating layer
may include patterning the plurality of passivation layers and
exposing an upper surface of the substrate, forming a sacrificial
layer for forming the nozzle on the exposed substrate, forming a
heat dissipating layer on the plurality of passivation layers, and
removing the sacrificial layer and forming the nozzle.
[0030] The sacrificial layer may be formed of a photoresist.
[0031] The heat dissipating layer may be formed by electroplating,
and the thickness of the heat dissipating layer may be greater than
about 10 .mu.m.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The above and other features and advantages of the present
invention will become more apparent to those of ordinary skill in
the art by describing in detail exemplary embodiments thereof with
reference to the attached drawings in which:
[0033] FIGS. 1 through 4 illustrate various structures of
conventional ink-jet printheads using the back-shooting method;
[0034] FIG. 5 illustrates a plan view of an ink-jet printhead
according to an embodiment of the present invention;
[0035] FIG. 6 illustrates a cross-sectional view taken along line
VI-VI' of FIG. 5; and
[0036] FIGS. 7 through 17 illustrate stages in a method for
manufacturing an ink-jet printehad according to an embodiment of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0037] Korean Patent Application No. 2003-8005, filed on Feb. 8,
2003, and entitled: "Ink-Jet Printhead and Method for Manufacturing
the Same," is incorporated by reference herein in its entirety.
[0038] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the invention are shown. The invention
may, however, be embodied in different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. In the drawings, the
thickness of layers and regions are exaggerated for clarity. It
will also be understood that when a layer is referred to as being
"on" another layer or substrate, it can be directly on the other
layer or substrate, or intervening layers may also be present. In
addition, it will also be understood that when a layer is referred
to as being "between" two layers, it can be the only layer between
the two layers, or one or more intervening layers may also be
present. Like reference numerals refer to like elements
throughout.
[0039] FIG. 5 illustrates a plan view of an ink-jet printhead
according to an embodiment of the present invention. Referring to
FIG. 5, the ink-jet printhead includes ink ejecting portions 103
disposed in two rows and bonding pads 101, each of which is
electrically connected to a corresponding one of the ink ejecting
portions 103. Each ink ejecting portion 103 includes a nozzle 104
and an ink chamber 106. In FIG. 5, the ink ejecting portions 103
are disposed in an exemplary two rows. The ink ejecting portions
103 may alternately be disposed in one row or in three or more rows
to improve printing resolution.
[0040] FIG. 6 illustrates a cross-sectional view taken along line
VI-VI' of FIG. 5.
[0041] The structure of an ink-jet printhead according to the
embodiment of the present invention will be described in detail
with reference to FIG. 6.
[0042] First, an ink chamber 106, which is to be filled with ink,
having a substantially hemispherical shape is formed on an upper
surface of a substrate 100. Here, a silicon wafer that is widely
used to manufacture integrated circuits (ICs) may be used as the
substrate 100.
[0043] A restrictor 108 for supplying ink to the ink chamber 106 is
perforated through a bottom surface of the substrate 100 and a
bottom surface of the ink chamber 106 to be perpendicular to the
bottom surface of the ink chamber 106. Preferably, the restrictor
108 has a length of about 200-750 .mu.m. The restrictor 108 is an
ink passage that provides communication between an ink reservoir
200 formed on the bottom surface of the substrate 100 and the ink
chamber 106 to be filled with ink to be ejected. Thus, unlike a
conventional ink-jet printhead that has a structure in which ink is
supplied to an ink chamber through a manifold and an ink channel,
the ink-jet printhead according to the present invention directly
supplies ink to the ink chamber 106 from the ink reservoir 200
through the restrictor 108.
[0044] A nozzle plate 120 is formed on the substrate 100 and forms
an upper wall of the ink chamber 106. The nozzle plate 120 is
formed of a plurality of material layers stacked on the substrate
100. The plurality of material layers includes first, second, and
third passivation layers 121, 123, and 125, and a heat dissipating
layer 126. A heater 122 is disposed between the first passivation
layer 121 and the second passivation layer 123. A conductor 124 for
supplying a current to the heater 122 is disposed between the
second passivation layer 123 and the third passivation layer
125.
[0045] The first passivation layer 121 is a lowermost material
layer of the plurality of material layers that are components of
the nozzle plate 120, and is formed on the upper surface of the
substrate 100. The first passivation layer 121 is a material layer
for providing insulation between the heater 122 formed on the first
passivation layer 121 and the substrate 100 formed under the first
passivation layer 121 and for providing passivation of the heater
122. The first passivation layer 121 may be formed of a material
selected from SiO.sub.2, Si.sub.3N.sub.4, SiC, Ta, Pd, Au, TaO,
TaN, Ti, TiN, Al.sub.2O.sub.3, CrN, and RuO.sub.2, or a stack
material thereof.
[0046] The heater 122, which heats ink in the ink chamber 106, is
disposed on the first passivation layer 121 and surrounds a nozzle
104. The heater 122 is formed of a resistance heating material,
such as TaAl, TiN, CrN, W, or polysilicon.
[0047] The second passivation layer 123 is formed on the first
passivation layer 121 and the heater 122. The second passivation
layer 123 is a material layer for providing insulation between the
conductor 124, formed on the second passivation layer 123, and the
heater 122, formed under the second passivation layer 123, and for
providing passivation of the heater 122. The second passivation
layer 123 may be formed of the same material as the first
passivation layer 121.
[0048] The conductor 124, which is electrically connected to the
heater 122 and applies a pulse current to the heater 122, is formed
on the second passivation layer 123. A first end of the conductor
124 is connected to the heater 122 via a contact hole formed in the
second passivation layer 123. A second end of the conductor 124 is
electrically connected to a bonding pad (101 of FIG. 5). The
conductor 124 may be formed of metal having good conductivity, for
example, aluminum (Al) or an aluminum alloy.
[0049] A third passivation layer 125 is formed on the second
passivation layer 123 and the conductor 124. The third passivation
layer 125 may be formed of the same material as the first and
second passivation layers 121 and 123.
[0050] A heat dissipating layer 126 is formed on the third
passivation layer 125. The heat dissipating layer 126 is an
uppermost material layer of the plurality of material layers that
are components of the nozzle plate 120 and dissipates heat
generated by the heater 122 and heat remaining around the heater
122. Thus, preferably, the heat dissipating layer 126 is formed of
a metallic material having good thermal conductivity, such as Ni,
Fe, Au, Pd, or Cu. The heat dissipating layer 126 is formed to have
a relatively larger thickness of greater than about 10 .mu.m by
electroplating the above-described metallic material. To perform
the electroplating, a seed layer (not shown) for electroplating of
the above-described metallic material may be formed between the
third passivation layer 125 and the heat dissipating layer 126. The
seed layer may be formed of a metallic material having good
electrical conductivity, such as Cr, Ti, Ni, or Cu.
[0051] Meanwhile, the nozzle 104, through which ink is ejected from
the ink chamber 106, vertically perforates the nozzle plate 120 at
a position corresponding to a center of the ink chamber 106. A
lower portion of the nozzle 104 has a cylindrical shape and is
formed in the first, second, and third passivation layers 121, 123,
and 125. An upper portion of the nozzle 104 has a tapered shape
such that a diameter thereof decreases as the nozzle 104 extends
toward an outlet, and is formed in the heat dissipating layer 126.
When the upper portion of the nozzle 104 has a tapered shape, a
meniscus of the surface of ink is more quickly stabilized after ink
is ejected.
[0052] Hereinafter, an operation of ejecting ink in the ink-jet
printhead having the above structure will be described.
[0053] First, when a pulse current is applied to the heater 122 via
the conductor 124 in a state in which ink fills the restrictor 108,
the ink chamber 102, and the nozzle 104, the heater 122 generates
heat. Heat is transferred to ink in the ink chamber 106 through the
first passivation layer 121 formed under the heater 122. As a
result, ink is boiled, and a bubble is generated in ink. The bubble
expands due to a continuous supply of heat. As a result, ink is
ejected through the nozzle 104. In this case, due to the restrictor
108, flow resistance is increased in a direction of bubble growth.
Thus, energy of a bubble may be more effectively used to eject ink
from the ink chamber 106.
[0054] Next, when the expanded bubble reaches a maximum size and
the applied current is cut off, the bubble contracts and collapses.
When this occurs, a negative pressure is applied to ink in the ink
chamber 106 such that ink in the nozzle 104 is returned to an
interior of the ink chamber 106. Simultaneously, ink ejected
through the nozzle 104 is separated from ink in the nozzle 104 by
an inertia force and is ejected in droplet form.
[0055] Finally, when the negative pressure in the ink chamber
disappears due to a surface tension acting on a meniscus formed in
the nozzle 104, ink ascends toward an outlet end of the nozzle 104.
As such, the ink chamber 106 is refilled with ink supplied from the
ink reservoir 200 through the restrictor 108. After an ink refill
operation is completed and the ink-jet printhead is returned to an
initial state, the above-described operation is repeated.
[0056] Hereinafter, a method for manufacturing an ink-jet printhead
according to an embodiment of the present invention will be
described.
[0057] FIGS. 7 through 17 illustrate stages in a method for
manufacturing an ink-jet printehad according to an embodiment of
the present invention.
[0058] First, referring to FIG. 7, a silicon wafer is processed and
is used as the substrate 100. A silicon wafer is widely used to
manufacture semiconductor devices, and thus, is effective in mass
production of a printhead.
[0059] FIG. 7 illustrates only a portion of a silicon wafer. An
ink-jet printhead according to the present invention may be
manufactured as several tens to hundreds of chips in a single
wafer.
[0060] The first passivation layer 121 is initially formed on the
upper surface of the substrate 100. The first passivation layer 121
may be formed of a material selected from SiO.sub.2,
Si.sub.3N.sub.4, SiC, Ta, Pd, Au, TaO, TaN, Ti, TiN,
Al.sub.2O.sub.3, CrN, and RuO.sub.2, or a stack material
thereof.
[0061] Next, as shown in FIG. 8, the heater 122 is formed on the
fist passivation layer 121 formed on the upper surface of the
substrate 100. The heater 122 is formed by depositing a resistance
heating material, such as TaAl, TiN, CrN, W, or polysilicon, over
the entire surface of the first passivation layer 121 to a
predetermined thickness and patterning a deposited resultant in a
ring shape.
[0062] Subsequently, as shown in FIG. 9, the second passivation
layer 123 is formed on top surfaces of the first passivation layer
121 and the heater 122. The second passivation layer 123 may be
formed of the same material as the first passivation layer 121.
[0063] Next, as shown in FIG. 10, the conductor 124 is formed on
the second passviation layer 123. Specifically, the conductor 124
may be formed by partially etching the second passivation layer
123, forming a contact hole through which part of the heater 122,
that is, a portion of the heater 122 to be connected to the
conductor 124, is exposed, depositing metal having good electrical
conductivity, such as aluminum (Al) or an aluminum alloy, on the
top surface of the second passivation layer 123 to a predetermined
thickness using sputtering and patterning a deposited
resultant.
[0064] Next, as shown in FIG. 11, the third passivation layer 125
is formed on the second passivation layer 123 and the conductor
124. The third passivation layer 125 may be formed of the same
material as the first and second passivation layers 121 and
123.
[0065] Subsequently, as shown in FIG. 12, the first, second, and
third passivation layers 121, 123, and 125 are etched to expose the
upper surface of the substrate 100, thereby forming a lower portion
of the nozzle 104. Specifically, the lower portion of the nozzle
104 may be formed by sequentially etching the third passivation
layer 125, the second passivation layer 123, and the first
passivation layer 121 within an interior of the ring-shaped heater
122 using reactive ion etching (RIE).
[0066] Next, as shown in FIG. 13, a sacrificial layer 130 for
forming the nozzle 104 is formed on the exposed substrate 100. The
sacrificial layer 130 is formed of a photoresist. Specifically, the
photoresist is coated over the entire surface of a resultant of
FIG. 12, and a coated resultant is patterned in a predetermined
shape so that only photoresist in a location that corresponds to a
portion where the nozzle 104 is to be formed remains.
[0067] Subsequently, although not shown, a seed layer for
electroplating the heat dissipating layer 126 of FIG. 14 is formed
on a top surface of the third passivation layer 125. For
electroplating, the seed layer may be formed by depositing metal
having good conductivity, such as Cr, Ti, Ni, or Cu, to a thickness
of about 500-2000 .ANG. through sputtering.
[0068] Next, as shown in FIG. 14, the heat dissipating layer 126
formed of a metallic material having a predetermined thickness is
formed on a top surface of the seed layer. The heat dissipating
layer 126 may be formed by electroplating metal having good thermal
conductivity, such as Ni, Fe, Au, Pd, or Cu, on the top surface of
the seed layer. In this case, preferably, the thickness of the heat
dissipating layer 126 is greater than about 10 .mu.m. Meanwhile, a
surface of the heat dissipating layer 126 after electroplating is
completed is uneven due to material layers formed under the heat
dissipating layer 126. Thus, the surface of the heat dissipating
layer 126 may be planarized by a chemical mechanical polishing
(CMP) process.
[0069] Subsequently, as shown in FIG. 15, the sacrificial layer 130
is etched to form the nozzle 104. As such, the nozzle plate 120
formed of a plurality of material layers is formed.
[0070] Next, as shown in FIG. 16, a bottom surface of the substrate
100 is etched to form the restrictor 108. The restrictor 108 may be
formed by etching the bottom surface of the substrate 100 using
inductively coupled plasma (ICP). Preferably, a length of the
restrictor 108 is about 200-750 .mu.m. Meanwhile, the restrictor
108 may be formed by wet etching. In this case, for a next process,
a passivation layer may be deposited on the bottom surface of the
substrate 100 on which the restrictor 108 is formed. The
passivation layer is an etch mask for etching silicon and may be
formed of a polymer, such as C.sub.xH.sub.y, C.sub.xF.sub.y, or
C.sub.xH.sub.yF.sub.2, or an insulating material, such as
SiO.sub.2, Si.sub.3N.sub.4, or SiC.
[0071] Next, as shown in FIG. 17, the ink chamber 106 to be filled
with ink is formed on the upper surface of the substrate 100. The
ink chamber 106 may be formed by isotropically etching the upper
surface of the substrate 100 exposed through the nozzle 104.
Specifically, the ink chamber 106 is formed by dry etching the
surface of the substrate 100 using an etch gas, such as an
XeF.sub.2 gas or a BrF.sub.3 gas. In this case, the ink chamber 106
has a substantially hemispherical shape and is in communication
with the restrictor 108.
[0072] As described above, the ink-jet printhead and the method for
manufacturing the same according to the embodiment of the present
invention have the following advantageous effects. First, an ink
chamber and a restrictor are formed on a substrate such that an
efficiency of a printhead using a back-shooting method is improved.
Second, a portion of the substrate is etched, thereby forming the
ink chamber such that a restriction on an operating frequency
caused by a large ink chamber is removed. Third, a manifold formed
on the substrate in the prior art is removed such that a more
uniform restrictor is manufactured. As such, the yield of the
printhead is improved, and a difference in performance between
nozzles in the same chip is reduced. Fourth, a process of
manufacturing the ink-jet printhead is simplified, and an
additional device other than a conventional device for
manufacturing an ink-jet printhead is not added, thereby reducing
costs for the restrictor.
[0073] Exemplary embodiments of the present invention have been
disclosed herein and, although specific terms are employed, they
are used and are to be interpreted in a generic and descriptive
sense only and not for purpose of limitation. For example, although
an exemplary material used in forming each element of an ink-jet
printhead according to the present invention has been described, a
variety of materials may be used to form elements. For example, a
variety of materials having good processing properties other than
silicon may be used to form a substrate. Similarly, a variety of
materials may be used to form a heater, a conductor, a passivation
layer, or a heat dissipating layer. In addition, although an
exemplary method for depositing and forming each material has been
described, a variety of deposition and etch methods may be applied
to an ink-jet printhead according to the present invention.
Further, specific values exemplified above may be varied within a
range where the ink-jet printhead can operate normally. In
addition, the order of each step of the method for manufacturing
the ink-jet printhead may be varied. Accordingly, it will be
understood by those of ordinary skill in the art that various
changes in form and details may be made without departing from the
spirit and scope of the present invention as set forth in the
following claims.
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